This invention relates to a method for separating dies on a wafer.
Currently wafers are diced using a scribe and break technique or a semiconductor-dedicated saw. Scribe and break technique uses a diamond scribe to create scribe marks in the alleys (i.e., scribe streets) between dies on a wafer. A special xe2x80x9cbreaking toolxe2x80x9dxe2x80x94typically an anvil above a doctor bladexe2x80x94snaps the wafer into discrete dies.
Dicing using a saw requires the wafer to be placed on a tape that is stretched taut across a round hoop. The hoop and the wafer are loaded into the saw and the circular spinning blade is moved back and forth to cut the alleys between the dies.
The width of the alley necessary to accommodate the scribe or the saw is about 100 microns. If the active area on a die is 160,000 square microns (400 microns on a side), then the total area of the die including the 50 micron alley around each die is 250,000 square microns, or a 57% increase over the total active area. If a 10 micron alley is added around the die, then the total die area becomes 168,100 square microns, or a 5.1% increase in area. The difference between a 100 micron alley and a 10 micron alley gives approximately 33% saving in area. Thus 33% more die can be produced on the same wafer.
Thus, what is needed is a method to separate dies on a wafer using smaller alleys.
In one embodiment of the invention, a method for separating dies on a wafer structure includes forming channels around the dies on a first side of the wafer structure, mounting the first side of the wafer structure to a plate having a first adhesive, and removing material from a second side of the wafer structure until the channels are exposed on the second side of the wafer structure. At this point, the dies are separated but held together by the first adhesive on the plate. The method further includes mounting a second side of the wafer structure to a second adhesive and dismounting the plate from the first side of the wafer structure. In one embodiment, the plate is dismounted by exposing UV radiation through the plate to the first adhesive so the first adhesive looses its adhesion to the wafer structure. At this point, the dies are held together by the second adhesive. The method further includes picking up the individual dies from the second adhesive.